Draft hood



Nov. 23, 1954 .1. w. MILLER' ETAL 2,695,,M6

DRAFT HOOD Filed July 12, 1949 2 Sheets-Sheet l N VEN TOR. Jo/M/ W. AM 5%? Nov. 23, 1954 J. w. MILLER ET AL 2695mm DRAFT HOOD Filed July 12, 1949 2 Sheets-Sheet 2 along the line 3-3 of United States Patent Ofiice 2,695,016 Patented Nov. 23, 1954 2,695,016 DRAFT HOOD Application July 12, 1949, Serial No. 104,271 20 Claims. (21. 126-607) This invention relates to a draft hood and more particularly to a draft hood which is especially useful for a gas fired heater.

A gas heater is organized so as to operate with maximum efliciency with a substantially zero draft at the last outlet from the radiating structure of the heater. Tests are run so as to be sure that this condition exists and the tests must show that the heater operates with a zero draft at this point when the draft in the flue varies from a positive draft to as much as .15 inch of water of negative draft. The function of the hood is to handle these drafts and still keep a substantially zero draft at the outlet of the heater. In order to do this the structure of the draft hood should be such that the draft through the draft hood into the flue can vary without affecting the draft at the outlet of the heater.

It is an object of this invention to produce a hood which will maintain a substantially zero draft at the last outlet from the radiating structure of the heater irrespective of the amount of the flue draft and irrespective of whether the flue draft is positive or negative. This is accomplished by means of a free opening at the bottom of the draft hood which is large enough so that the draft hood will at no time build up a back pressure and the surface of the hood on the inside over which the air and the products of combustion flow does not have any corners where eddy currents can develop.

This invention contemplates a draft hood which is of exceedingly simple structure, cheap to build, easy to install, and which has a flue outlet pipe which can be easily turned to either vertical or horizontal position or to any intermediate position, thus to readily connect into either a vertical or horizontal flue pipe or flue pipe positioned anywhere between horizontal and vertical position.

Fig. 1 is a front elevation showing our draft hood and taken along the line 1-1 of Fig. 2.

Fig. 2 is a side elevation partly in section showing our draft hood, and

Fig. 3 is an elevation of the flue Fig. 2.

Our draft hood is extremely simple and consists essentially of five parts all of which preferably, but not necessarily, are sheet metalstampings; namely, front member 1, back member 2, flue outlet pipe 3, retainer plate 4, and bafile 30;

Front member 1 comprises a front upright wall 5 which is preferably vertical, opposed side walls 6, top wall 7 which is preferably planar, and flange 8 which extends around the top and two sides of front member 1. Front member 1 is preferably a single integral stamping and, for reasons pointed out below, the included angle A between top wall 7 and the vertical runs 9 of flange 8 is 45". Front member 1 is provided with an open bottom which provides an opening 10 through which air is drawn upwardly and thence through the flue outlet 3, as indicated by the arrows, so that the draft on the heater will be substantially zero. The top 7 is provided with a circular opening 11.

The flue outlet pipe 3 is provided with a circular flange 12 at its inner end and an elliptical outlet 14 at its outer end. The inside circumference 15 of flange 12 is preferably approximately equal to the circumference of circular opening 11 so that circular flange 12'overlaps top 7 completely around opening 11. The flue outlet pipe is outlet pipe taken a retainer ring 4 having a circular opening'lfi through which flue outlet pipe 3 passes. Retainer ring 4 overlaps flange 12 of flue outlet pipe 3 and is secured to the top 7 in any suitable manner. By way of illustration, retainer plate 4 is provided with four integral tongues 17 which are struck out of the retainer plate and pass through corresponding cooperating openings in top 7 and then clinched over to lock the retainer plate to top 7. Flange 12 and retainer. plate 4, of course, are centered with respect to opening 11 in top 7. The portion of top 7 surrounding opening 11 cooperates with retainer plate 4 to provide a circular groove in which flange 12 is free to slide, thus providing a swivel connection between top 7 and flue outlet pipe 3.

The axis A of the flue outlet pipe is positioned at an angle of 45 with respect to a plane passing through flange 12. This is illustrated in full line showing of Fig. 2. Hence, if flue outlet pipe 3 is turned or swivelled so that flange 12 turns in its swivel mounting between top 7 and retainer plate 4, the flue outlet pipe will be positioned, as shown in the dotted lines, Fig. 2, so that the axis A of pipe 3 is substantially vertical. As shown in the full lines in Fig. 2, the flue gases will flow outwardly in a substantially horizontal path whereas in the dotted line showing the flue gases will flow in a substantially vertical direction. Flue outlet pipe 3 can, of course, be adjusted to any intermediate position between the horizontal and the vertical by turning flange 12 less than 180 from the horizontal position, shown in the full lines of Fig. 2.

A heat shield 20 in the form of a sheet metal plate having side flanges 21 is positioned within front 1 parallel to, but spaced from, wall 5 and flanges 21 are welded to the side walls 6 of the front.

The hood back 2 is also preferably in the form of a sheet metal stamping having an inclined bottom wall 22, a vertical rear wall 23, top wall 24 and side Walls 25. The front of back member 2 is open. Member 2 is provided with a peripheral flange 26 extending completely around the open front of the back member and spot welded as at 27 in juxtaposition to flange 8. Back wall 23 is provided with a circular opening 28 having an inwardly turned circumferential flange 29.

The draft hood is provided with a baffle 30 in the form of a single sheet of metal having side flanges 31 welded to the inner faces of sides 6 and 25 and has vertically positioned vanes 32 struck out of the same to provide openings 33. The bafile 30 is such that when an air flow comes from the flue '3 into the hood, the flow will be turned so that it proceeds out of the bottom opening 10 of the hood. This bottom opening 10 is larger in area than either the cross-sectional area of flue pipe 3 or the area of outlet opening 11 so that opening 10 never acts as a restriction with respect to flue 3 and opening 11. Thus, when the air flow is from flue 3 into the draft hood, opening 10 will not create a back pressure and when the flow is from the hood into the flue 3, opening 10 will never create a vacuum or draft at the heater outlet 28.

In our hood the air flow can enter the hood from flue 3 either horizontally or vertically or from some intermediate direction depending upon the position of flue outlet pipe 3. Our baflle is made so that where the flow is from the flue into the hood the vanes 32 direct the air toward the open end 10 of the hood in any position of the flue outlet pipe 3. It should be noted that baflle 30 is long enough to cover the outlet '28 from the heater 35 when viewed through the hood outlet opening 11. The

baflleis set high enough with respect to opening 28 so that a flow of gas into the hood when the flue pipe 3 discharges horizontally will not eddy over the top of the baflle and build up a pressure behind the baflle at the outlet of the heater into the hood. The baffle 30 is positioned substantially midway between heater outlet 28 and hood outlet 11. The vanes 32 are positioned in vertical parallel planes spaced from each other in stepped relation from thetop' of the baflle downwardly and toward the front wall of the hood and the major portion of the baffle 30 is positioned above the center of opening 28.

The function of baflie 30, of course, is to permit'the outward travel through openings 33 of the flue gases, as indicated by the arrows, and prevent any downdraft coming through flue outlet pipe 3 in a reverse direction from reducing the draft'atthe outlet from the heater to .a..negative draft. Any .downdraft entering the hood through outlet pipe 3 will, be diverted vertically downwardly by vanes 32 and thence out through bottom opening in the base of the-hood.

From the, above it; is evident thatwehave disclosed a draft hood which isof extremely simple and inexpensive construction and-with a flue out-let;.pipe.- which, isxreadily adaptable to connect into a horizontal fluewpipeor a vertical flue pipe or-a fluepipe positionedat any-angle :between the horizontal and 'the vertical.

The assembly of-our draft hoodto ag'heaterc-is illustrated in Fig. 2. InjFig, 2;we have :shown a fragment of a heater comprisinga-;heat;exchanger-35 which ispref- -erably gas fi1'daI1d';-lS provided with :a-circular .outlet 36 over which -flange;29;1of:our draft hood telescopes. The back wall 38 of the heater casing isprovide'dxwith a rectangular'opening 39 into-which theback member "2-of the draft hood projects with-the Iflange; 26 overlap- :ping the outer face ;of back .38 :ZIl'Otllld opening ;39.

The draft hood 1s-reta1ned .inposition by ,a pair: of bolts '40 which pass through elongated openings 41-in flanges 9 and cooperating openings ,in back 38.

Thus, in operationpthe products of combustion pass from the heatexchanger.,35 (which,1of;.course, is in communication' with :a conventional icombustion .chamber withinthe heatennot shown). through outlet .36, 28 into our draft hood and then either horizontally -.outwardly through flue outlet-pipez3 .Wheninthehorizontal position, full lineshowing, .Fig. 2, orvertically upwardly when the flue outlet pipe 3,-is :in the dotte'dlineposition, Fig..2. At the same time; air from the .roornor area being heated passes upwardly through ,inlet 10in the bottom wall of our draft 1hood, thenoutwardly through pipe 3 to thereby reduce the draft at'the outlet of the heater to substantially zero.

It will be noted that as -.pipe' 3 is swivelled upon top -7 'thatthe axis A describes a" cone having its apex positioned in a line through 'thewcenter of openings 11, which are concentric.

-We claim:

1. A draft'hoodnadapted to connect gas'burning heating apparatus into afluefor carrying away the products of combustion, comprising aihousinghaving front, rear, side and top walls, the-bottom wall of said housing'being provided with anair inlet opening, there being an '-inlet opening in the rear wall for theproducts'of'combustion and an outlet opening in 'the:top -wall,-said topwall being inclined downwardly toward the front wall, afflueout-let pipe 7 of elliptical crosssect-ionysaid outletpipe having .a generally circular inner end swivelled in the plane thereof on said top wall aboutsaid-outletopening-on-an axis perpendicular to said top wall, the inner end-of said outlet pipe being positioned in a'plane inclined atan angle of substantially 45 to ;the',longitudinal axis of said flue outlet pipe and the plane-of the inner; end'of said outlet pipe and said top wall-being inclinedjto-the vertical at a corresponding angle wherebysaidilueoutlet pipe can be swivelledabout said outlet opening into horizontal or vertical or intermediate positions.

2. The draft hood-claimed in .claim ,1 whereinthe inner end of said outlet pipe is provided .with ansoutwardly turned circular planar {flange positioned in,a plane inclined at an angle of substantially 45 to the longitudinal axis of said flue outlet pipe, said circular flange overlying the top wall around-thecircurnference 'of said outlet opening, and means for" holdingsaid-circular planar flange in rotational sliding-relation againstjthe top wall of said housing-whereby 'theflue'out-let-pipe can be swivelled about said outlet opening.

3. The draft hoodclaimed in claim 2 wherein said means comprises a retainer plate having a-circular opening therein secured-to said top wall and overlying in rotational sliding relation=the-said circumferential flange on said flue outletpipe.

4. The draft hood claimed-in claim ,3 wherein the air inlet opening inthe bottom -wall-of said "drafthood is positioned below the'flue outlet-opening in the top .walland wherein the products of-combustion -inlet opening is positioned in said rear wall offset from vthe air inlet andflue outletopenings.

SQ'The draft hood claimed in claim --4 including a. peripheral flange-extending :around saidhousing 'in a .plane spaced between.saidfrontandrear walls with the products :of combustion opening positioned -on the rear &4 wall side of said flange and the air inlet opening and flue outlet-openingpositioned on the -front-wall side -of said flange.

6. The draft hood claimed in claim 1 including a pcripheral flange extending around said housing in a plane intermediate said rear and front walls and adapted to abut a wall in said heating apparatus for locating the draft hood with respect to said heating apparatus.

7. A draft hood adapted to connect a gas burning heating apparatus into a flue .for carrying away the productsg'of combustion, comprising a housing consisting 'of'front and rear sections, the front section comprising a sheet metal stamping having a front wall, a top wall inclined downwardly toward said front wall and having an outlet opening therein, and side walls, and a flange extending along theouter edges of said side and top walls, said rear section comprising a rear wall having an inlet opening therein, top, bottom and side walls, and a flange-extendingaroundi the periphery of the top, bottom and side walls and'secured-in juxtaposition to thejflange on the front section, a flue outlet pipe of elliptical cross :sectionhaving-a generally circular inner endswivelled on ;said inclined top-wall about said outlet opening,'the inner end of said'outlet pipe -being;-positioned in a-plane inclined at an angle of substantially 45 to the longitudinal axisof.said flue outlet pipe-and the plane of said top vwall rand'outlet opening =being;.-inclined to the vertical rat :a *correspondingangle whereby; said flue outlet pipe .can be: swivelled into-horizontal,vertical or intermediate positions.

-8. In :a :gas -burning :heating apparatus including a he exchanger having'an :outlet for the products of combustion and ,a'casingsaround said heat exchanger in spaced relation therewith and having an opening in one of its walls :adjacent' the'outlet of said heat exchanger, a drafthood mounted in the said opening in the wallof said casingand adapted to connect the outlet --of saidheat'exchangerxinto. aflue for carrying away the :products of combustion, said draft hood comprising a :housing having -atfrontwall, rear wall, side walls, and ;a top'wall'inclineddownwardly towardzsaid front wall,

" there being :an .inlet in the .rear wall arranged for connection .zwi'th *theoutlet -:of said heat exchanger, a

peripheral-flange extending varound the housing between the front and rear wa'llssand adapted to -.overlie the .-'said ;wall of said rcasing around theopening in the wall ofsaid casingi'forilocatingr'the draft hood with respect .torthe heat .=exchanger,:.there being an air inlet opening in'ithe bottom-'of--said-'draft-hood-onthefront wall side rofsaidperipheral'rflange, :a flue outlet-opening in the top -:wall:also 'onithe front .wallside ofsaid peripheral 'fiange, and a flue outlet pipe=of elliptical cross section having a generally circular inner end swivelled on said inclined "topwall about saidoutlet-opening, the inner-end of said outlet pipe being positioned in a plane inclined at an angle of'substantially 45 to the longitudinal axis of said flue outlet pipe and the plane of said topwall and outlet opening' being inclined to the vertical at a corresponding angle whereby said 'flue outlet pipe can be swivelled 'into horizontal, vertical or intermediate posi- =tions.

*9. The combination claimed inclaim 8 wherein the inner end of said outlet-pipe is provided with an'outwardly turned circular planar flange positioned in a plane inclined to the longitudinal axis of said flue outlet pipe, said circular flange ove'flyingthe "top wall around the circumference of said outlet opening, and means for holding said circumferential flange in rotational sliding relation against the top wall of said'housing whereby thefflue outletpipe can be swivelled about said outlet opening.

'10. The draft hood "claimed in claim '1 including a 'batflepositioned in said-hood between the inlet opening in the rear wall and the outlet opening in thetop wall,

said baflie comprising a plurality of spaced substantially vertical and substantially parallel-vanes positioned in stepped relation from the top downwardly and toward the front wall of said hood.

1l.'The drafthood claimed in claim 10 wherein the battle is positioned substantially midway between the inlet opening-in the rear wall and the -outlet opening in the top' wall and the major portion-of the baffle is above the center of said inlet opening.

12. The draft 'hood claimed in claim 7 including -a baffle positioned in-said hood between the inlet-opening -in-the rear :wall'and'the outleta opening in the'top wall,

said baflie comprising a plurality of spaced substantially vertical and substantially parallel vanes positioned in stepped relation from the top downwardly and toward the front wall of said hood.

13. The draft hood claimed in claim 12 wherein the baffle is positioned substantially midway between the inlet opening in the rear wall and the outlet opening in the top wall and the major portion of the baffle is above the center of said inlet opening. 7

14. The draft hood claimed in claim 1 including a downwardly and forwardly inclined batfle positioned in said hood between said top and rear walls, said baffle being dimensioned and positioned within said hood to completely overlie the inlet opening in said rear wall when viewed in a direction normal to the plane of said top wall whereby direct flow of gas and air between said inlet opening in said rear wall and said outlet opening is prevented.

15. A draft hood adapted to connect gas burning heating apparatus into a flue for carrying away the products of combustion, comprising a housing having front, rear, side and top walls, the bottom wall of said housing being provided with an air inlet opening, there being an inlet opening in the rear wall for the products of combustion and an outlet opening in the top wall, said top wall being inclined downwardly toward the front wall at an angle of substantially 45 to the vertical, a flue outlet pipe having a circular flange at its inner end, means on said top wall surrounding said outlet opening and forming a swivel connection with said circular flange, said circular flange at the inner end of said outlet pipe being positioned in a plane inclined at an angle of substantially 45 to the longitudinal axis of said flue outlet pipe whereby said flue outlet pipe can be swivelled about said outlet opening into horizontal or vertical or intermediate positions.

16. The draft hood claimed in claim wherein said means comprises a retainer plate on said top wall having a circular opening therein, said retainer plate being secured to said top wall in overlapping relation to said circular flan e.

1 7 The draft hood claimed in claim 15 wherein the flue outlet pipe is of elliptical cross section in a plane normal to the longitudinal axis of said flue outlet pipe, the inner end of said flue outlet pipe provided with said circular flange defining a plane, said outlet opening being circular and generally concentric with the circular opening at the inner end of said flue outlet pipe.

18. A draft hood adapted to connect gas burning heating apparatus into a flue for carrying away the products of combustion, comprising a housing having front, rear, side and top walls, the bottom wall of said housing being provided with an air inlet opening, there being an inlet opening in the rear wall for the products of combustion and an outlet opening in the top wall, said top wall being inclined downwardly toward the front wall at an angle of substantially 45 to the vertical, a flue outlet pipe having its inner end supported on said top wall for relatively free rotation about said opening, the inner end of said outlet pipe being positioned in a plane inclined at an angle of substantially 45 to the longitudinal axis of sa d flue outlet pipe and the plane of the inner end of sand outlet pipe being inclined to the vertical at a correspond ing angle, said pipe being freely rotatable about said outcircular opening in said inclined let opening on an axis perpendicular to the plane of said 6 top wall 1nto horizontal or vertical positions.

19. A draft hood adapted to connect a gas burning heating apparatus into a flue for carrying away the products of combustion, comprising a housing consisting of front and rear sections, the front section comprising a sheet metal stamping having a front wall, a top wall inclined downwardly toward said front wall at an angle of substantially to the vertical and having an outlet opening therein, and side walls, and a flange extending along the outer edges of said side and top walls, said rear section comprising a rear wall having an inlet opening therein, top, bottom and side walls, and a flange extending around the periphery of the top, bottom and side walls and secured in juxtaposition to the flange on the front section, a flue outlet pipe having its inner end supported on said inclined top wall about said opening, the inner end of said outlet pipe being positioned in the plane of said top wall and in a plane inclined at an angle of substantially 45 to the longitudinal axis of said flue outlet pipe and the plane of said outlet opening being inclined to the vertical at a corresponding angle, said flue outlet pipe being movable about said outlet opening on an axis perpendicular to the plane of said top wall into horizontal or vertical positions.

20. In a gas burning heating apparatus including a heat exchanger having an outlet for the products of corn bustion and a casing around said heat exchanger in spaced relation therewith and having an opening in one of its walls adjacent the outlet of said heat exchanger, a draft hood mounted in the said opening in the wall of said casing and adapted to connect the outlet of said heat exchanger into a flue for carrying away the products of combustion, said draft hood comprising a housing having a front wall, a rear wall, side walls, and a top wall inclined downwardly toward said front wall at an angle of substantially 45 to the vertical, there being an inlet in the rear wall arranged for connection with the outlet of said heat exchanger, a peripheral flange extending around the housing between the front and rear walls and adapted to overlie the said wall of said casing around the opening in the wall of said casing for locating the draft hood with respect to the heat exchanger, there being an air inlet opening in the bottom of said draft hood on the front wall side of said peripheral flange, a flue outlet opening in the top Wall also on the front wall side of said peripheral flange, and a flue outlet pipe having its inner end supported on said inclined top wall about said opening, the inner end of said outlet pipe being generally circular and positioned in a plane inclined at an angle of substantially 45 to the longitudinal axis of said flue outlet pipe and the plane of said outlet opening being inclined to the vertical at a corresponding angle, said flue outlet pipe being movable about said outlet opening on an axis perpendicular to said top wall into horizontal or vertical positions.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,257,240 Livar Sept. 30, 1941 2,313,933 Goerg Mar. 16, 1943 2,314,850 Woelfel Mar. 23, 1943 FOREIGN PATENTS Number Country Date 437,852 Germany Nov. 30, 1926 

